Art of coloring wood.



UNITED STATES- PATENT" orrron. 4.

WILLIAM AUGUSTIlS HALL, OF NEW YORK, Y.

'AR'I. 0F COLORING-. WOOD.

Specification of Letters Patent.

/ Patented Oct. 13, 1908.

Application filed February 15, 1908. Serial No. 416,114.

To all whom it may concern: y

Be it known that I, WILLIAM AUeUsTUs HALL, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented or discovered certain-new and useful Imexpensive and more portable apparatus than is necessarily employed in processes by which the wood is artlficially colored throughout by sub'ecting the wood to a vacuum process,

to wit draw the ai-r'therefrom, and then subsequently forcing the coloring matter into and throughout the wood by very high pressures in closed tanks or cylinders.'

In carrying the present invention into effect the 'wood is treated by first boiling the same in an aqueous coloring" solution which colors the wood by chemical action and which may be contained in an open vat or tank provided with steamv coils or other suitable means for heating the coloring solution, which must be of a highly penetrating character. In other words the process consists in first boiling the wood in an aqueous solution which darkens the same chemically and which boiling is effected at atmospheric pressure, so that the temperature of the said solution will be at or about 212 F., such boiling of the Wood in the penetrating chemical colorin solution being continued for a period sufficiently long to cause the wood under treatment to be impregnated throughout with said solution.

Thus for a moderately hard wood, like birch,

. required to cause the wood to become thoroughly saturated with the chemical coloring solution which must be of very high cap1llarity with an afiinity for the cellulose in the wood tissue, and which acts to color or darken the wood by the action-of the reagent in the solution upon the ligno-cellulose matter of the wood, and particularly so in the presence of heat.

- A good example of a highly penetrating coloring solution in which the wood is to be first boiled, for the purpose stated, is a salt of iron, preferably ferrous pyrolignite, which will stain the wood to a deep ayish brown when the wood is boiled therein. Also copperas may be employed, if desired. The I color produced by thus boiling the wood in a solution cont'aimn' "a salt of iron, as just stated, is. a grayis' brown and is not very desirable commercially and a further treatment of the wood order to produce'desired' commercial shades. To this end the wood, while it is still hot from the first boiling process, is subjected is therefore necessary in to the action of a" coloring solution which is [applied to the wood in a cold condition, and this second step in the process may be carried into effect either by drawin oii from the vat or receptacle the hot solutlon in which the wood is first boiled and immediately replacing the same with the cold coloring solution, or by removing the wood from the hot solution in the vat and then immediately immersing it in another vat or tank containing the cold coloring solution. The second solution in which the wood is treated may be either a salt or a coloring matter in solution, according to the shade desired. If the second solution be an alkaline salt, such as carbonate of soda or. ammonia, it will convert the grayish brown produced by the iron salt into a reddish brown, which is more desirable commercially. If a red color be desired a solution of dye-woodxor hemlock bark, or anhydrids of tannin may be employed; and it will therefore be understood that this second solution is not to be limited to any specific coloring material, but is a matter of selection, according to the shade or color desired.

When the wood, while still hot from the pand much more than does the air at the same temperature; whereas at temperatures lower than 212 F. air is expanded by heat to a much greater extent than water. In practice the lumber cannot be heated quite to 212 1*. throughout its inner parts, when boiled in a solution at atmospheric pressure, in which case the highest temperature of the solution is of course only about 212 l1, and the inner parts of the wood will not rise quite to this temperature; so that when the wood in its heated condition from the first boiling is subjected to the action of the cold coloring solution the latter will have a greater contracting efi'ect upon the air contained in the wood than upon the water or aqueous solution therein contained, resulting in the contraction or partial vacuum which draws the cold coloring solution into the wood as above stated. I

When it is not necessary that the wood, which is colored or darkened throughout by the first boiling process, should be colored throughout to the desired commercial shades; or when it is essential that commercial shades be imparted to the wood only to a depth of a quarter of an inch or so, such coloring will be eli'ected in a short time by permitting the wood to remain in the cold solution. Deep reds can be obtained in this way at relatively very small cost, due to the fact that a penetration of only about a quarter of an inch by the second solution is necessary; as the interior portions of the wood have been already colored to a dark shade by the first step of the process, so that if the interior portions of the wood become exposed by scratching or shrinkage there will be no particular contrast in color, and no light natural color will be exposed. This manner of coloring the wood is particularly desirable in the matching of deep ,red mahoganies or rosewoods, for the reason that all deep red coloring solutions are quite expensive, and economy in the use of such solutions is therefore necessary in order to enable the artificial product to be successfully sold in competition with the natural woods. But when it is desired that the deeper or redder commercial colors of the wood should extend throughout the same the second coloring solution, first applied cold, should be heated, and the wood should be boiled therein for one or more days; as this action will cause a more or less circulation of the coloring solution throughout the wood, so that the latter will become completely permeated thereby; such circulation or action serving to displace, to a greater or less extent, the first or chemically acting solution. Also in this manner one solution may be made to follow another solution into the wood without any drying of the wood between the difierent steps of the treatment, and without the removal either of the air eoipee I or the previous solution contained therein,

either by a mechanically applied vacuum, or by removal of the previous solution by drying or evaporation; so that the wood impregnated with one solution can be further impregnated with a second solution, and then, if desired, with a third, and so on, without any intermediate drying, or without removing the air mechanically; thereby greatly. lessening cost, in comparison with the vacuum and high pressure treatment, and enabling deep colors to be obtained by the action of one chemical upon another.

The second step of the process above described is very important for the reason that the grain or figure of the wood is but very slightly developed by the hot solution in which it is first boiled, but 'in the treatment by the second solution the grain or figure of the wood will be very largely developed, for the reason that the pigment of the coloring solution will naturally become deposited in the more porous portions or grain cells, if a dye coloring solution be employed; or if a solution acting chemically on the lignocellulose matter of the wood be employed the effect of such chemical action is much more pronounced in the more porous portions and grain cells than in the denser parts of the wood. This is largely due to the fact that this second solution, thus absorbed, remains to a larger extent in the porous portions of the Wood as long as the solution is at a low temperature, but if the wood so containing it be boiled then more or less diffusion of the color ensues.

Having thus described my invention or discovery I claim and desire to secure by lL-etters Patent i 1. The herein described process of coloring Wood, consisting in boiling the same at atmospheric pressure and at a temperature of or about 212 F. in a highly penetrating aqueous solution, to darken the body of the wood throughout, then subjecting the wood,

while still'hot, to the action of a cold coloring solution, so that, by contraction, the lustnamed solution will be drawn into those portions of the wood near the surfaces thereof to color such portions to any desired shade.

2. The herein described process of coloring wood, consisting in boiling the same at atmospheric pressure and at a temperature of or about 212 F. in a highly penetrating aqueous solution, to darken the body of the wood throughout, then subjecting the Wood, while still hot, to the action of a cold coloring solution, so that, by contraction, the lastnamed solution will be drawn into those poi"- tions of the wood near the surfaces thereof to color such portions to any desired shade, and then boiling the wood in the said second coloring solution to cause the wood to be colored throughout to the shade desired.

3. The herein described process of coloring wood, consisting in boiling the same at atmospheric pressure, and at a' temperature of or about 212 F., in a ferrous pyrolignite solution, to darken the body of the wood throughout, then subjectin thewood, while still hot, to the action o a cold aqueous alkaline coloring solution, so that, by contraction, the last-named solution will be drawn into those portions of the wood near the surfaces thereof to color such portions to any desired shade. 4

4. The herein described process of coloring wood, consisting in boiling the same at atmospheric pressure, and at a temperature of or about 212 F., in a ferrous pyrolignite solution, to darken the body of the wood throughout, then subjecting the wood, while still hot, to the action of a cold aqueous alkaline coloring solution, so that, by contraction, the last-named solution will be drawn into those portions of the wood near the surfaces thereof to color such portions to any desired shade, and then boiling the wood in the said second coloring solution to cause the wood to be colored throughout tothe shade desired.

In testimony ture, 1n presence of two witnesses.

WILLIAM AUGUSTUS HALL.

Witnesses:

ANNIE B. WALTERS, WALTER M. SOHEUMAKER.

whereof I afiix my, signa- 

